Permanent soil and subsoil measurement probe

Abstract

A device for monitoring an formation below the ground G containing a fluid such as CO 2 or methane comprising a measuring cell arranged in a cavity, can an F analyzer disposed on the surface and a sealed connection connecting measuring cell to the analyzer. The measuring cell comprises two chambers that can sealingly communicate with one another. The first chamber comprises a plurality of orifices allowing passage of the fluid into first chamber, at least two inner electrodes and fluid circulator. The second chamber is impervious to the fluid. Applications include monitoring of geological storages sites for gas such as CO 2 .

The invention claimed is: 
     
       1. A system for monitoring an underground formation containing a fluid comprising:
 least one measuring cell for placement in a cavity provided in the underground formation, an analyzer for placement on a ground surface of the underground formation, a sealed electrical connection for electrically connecting the at least one measuring cell to the analyzer, the at least one measuring cell including at least a first chamber, a second chamber which is impervious to entry of the fluid into the second chamber, and at least three sealed inner connectors which electrically connect the first chamber to the second chamber; and wherein the first chamber includes a plurality of orifices through which the fluid may pass into the first chamber from the formation, at least two inner electrodes electrically connected to at least two of the at least three sealed inner connectors, the sealed electrical connection being electrically connected to the inner connectors, and a fluid circulator electrically connected to the analyzer and to at least one of the connectors and to the sealed electrical connection and the first chamber is filled with a porous material having petrophysical and electrical properties. 
 
     
     
       2. A system as claimed in  claim 1 , comprising:
 at least two outer electrodes, two inner connectors connecting the two chambers, two sealed outer connectors disposed on at least one wall of the first chamber, the wall being in contact with the formation, the outer electrodes cooperating with the two sealed outer connectors, the outer electrodes being electrically connected to the analyzer through the connection which is electrically connected to the two inner connectors and the two outer connectors. 
 
     
     
       3. A system as claimed in  claim 1 , wherein:
 the sealed electrical connection includes an electrical power supply which supplies electrical power to the electrodes and the sealed electrical connection comprises a sealed sheath protecting at least the fluid circulator and the power supply. 
 
     
     
       4. A system as claimed in  claim 2 , wherein:
 the sealed electrical connection includes an electrical power supply which supplies electrical power to the electrodes and the sealed electrical connection comprises a sealed sheath protecting at least the fluid circulator and the power supply. 
 
     
     
       5. A system as claimed in  claim 1 , wherein the petrophysical properties are at least porosity and permeability, and the electrical properties are at least electrical conductivity. 
     
     
       6. A system as claimed in  claim 1 , wherein the sealed electrical connection, the chambers and the connectors comprise PTFE. 
     
     
       7. A system as claimed in  claim 2 , wherein the sealed electrical connection, the chambers and the connectors comprise PTFE. 
     
     
       8. A system as claimed in  claim 3 , wherein the sealed electrical connection, the chambers and the connectors comprise PTFE. 
     
     
       9. A system as claimed in  claim 4 , wherein the sealed electrical connection, the chambers and the connectors comprise PTFE. 
     
     
       10. A system as claimed in  claim 1 , wherein the analyzer includes at least one of a fluid analyzer and a resistivity meter. 
     
     
       11. A system as claimed in  claim 1 , wherein the fluid circulator includes at least a pipe, a fluid suction system and a fluid reflux system. 
     
     
       12. A system as claimed in  claim 1 , wherein the fluid circulator includes at least two pipes, a fluid suction system and a fluid reflux system. 
     
     
       13. A system as claimed in  claim 1 , wherein the underground formation is geological storage site for a gas including CO 2  or methane. 
     
     
       14. A system as claimed in  claim 11 , wherein the system is calibrated prior to injecting gas into a geological storage site.